High surface area zirconia by digestion of zirconium propoxide at different pH

Abstract

The microstructure of hydrous zirconia (ZrO2) prepared by the hydrolysis of zirconium propoxide followed by digestion at pH 1, 3 and 9 and the ZrO2 derived from this precursor have been studied. The undigested hydrous oxides formed plate-like aggregates with low porosity. After digestion at pH 9, the hydrous oxides became highly porous with surface areas up to 550 m2/g. Calcination at 500°C for 12 h results in ZrO2 with surface areas of more than 380 m2/g. ZrO2 formed after digestion in acidic medium had lower surface areas of less than 100 m2/g and were mixed in tetragonal and monoclinic phases. The water/propoxide ratio during gel formation influences the surface area of the resulting ZrO2. The thermal stability of the material is remarkable: ZrO2 resulting from long digestion retained up to 100 m2/g after successive heating to 900°C. The observed microstructural properties are attributed to the nature of the alkoxide precursor formed under different water/alkoxide ratios and to the effects of digestion under varying pH conditions. (C) 2000 Elsevier Science B.V. All rights reserved.